Tuesday reports had put the number of virus victims at 19.
Almost 1,000 people were quarantined for possible MERS on Wednesday night, pushing the overall number to 6,508, the Korea Herald newspaper said.
The number of confirmed cases has reached 162, the daily said.
Middle East Respiratory Syndrome is a viral respiratory disease caused by the MERS-coronavirus. The infection was first reported in 2012 in Saudi Arabia and subsequently spread to other countries.
There is currently no vaccine for MERS.